Ticket #23176: 23176.2.diff

wp-includes/js/media-editor.js

@@ -18 +18 @@
                                 if ( 'image' === props.type && ! props.alt ) {
                                         props.alt = props.caption || props.title || '';
                                         props.alt = props.alt.replace( /<\/?[^>]+>/g, '' );
+                                        props.alt = props.alt.replace( /[\r\n]+/g, ' ' );
                                 }
 
                                 return props;